Emission Computed Tomography (ECT) has been widely used in medicine for diagnosis and other purposes. Types of ECT include Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT). Positron emission tomography (PET) is a specialized radiology procedure that generates three-dimensional images of functional processes in a target organ or tissue of a body. Specifically, in PET studies, a biologically active molecule carrying a radioactive tracer is first introduced to a patient's body. The PET system then detects gamma rays emitted by the tracer and constructs a three-dimensional image of the tracer concentration within the body by analyzing the detected signals. Because the biologically active molecules used in PET studies are natural substrates of metabolism at the target organ or tissue, PET can evaluate the physiology (functionality) and anatomy (structure) of the target organ or tissue, as well as its biochemical properties. Changes in these properties of the target organ or tissue may provide information for the identification of the onset of a disease process before any anatomical changes relating to the disease become detectable by other diagnostic tests, such as computed tomography (CT) or magnetic resonance imaging (MRI).
A subject, such as a patient, may be scanned by an ECT scanner to obtain ECT images. When ECT is used for chest or upper abdomen examinations, respiratory and/or cardiac motions may lead to motion blur n the ECT images. It is desirable to provide systems and methods for reconstructing an ECT image with improved quality and reduced motion blur.